Molecular export from this structure is prevented 
Molecular export from this structure is prevented by retention sequences like KDEL. Vesicles are targeted to this organelle by COPI, and N-linked precursor oligosaccharides are key to one of its functions. One type of this organelle contains large amounts of calcium and mediates skeletal muscle (*) contraction. Grp78 and PDI are two major chaperone proteins located in this organelle. Lipid synthesis, glycosylation, and folding and tagging of proteins all occur in this organelle. For 10 points, name this organelle that is continuous with the cell membrane and comes in "rough" and "smooth" varieties.
Molecular export from this structure is prevented by retention sequences like KDEL.
{endoplasmic reticulum}